The present invention relates generally to video signal processing, and more particularly to techniques for recording broadcast programs or other types of video signals.
Conventional videocassette recorders (VCRs) and other types of video recording devices are generally provided with the capability of recording a broadcast, program for a preset recording time period. For example, a user may program such a device to record a broadcast program on a particular channel at a particular time, e.g., to record a two-hour movie scheduled to appear on channel 6 from 10pm-12pm on Nov. 25, 1999. A similar effect may be achieved by entering a so-called VCR+ code, which is a simpler approach in that it avoids the need for a user to enter specific information such as channel, date and time.
A significant problem with these and other conventional recording techniques is that the actual broadcast time of the desired program to be recorded often does not correspond exactly to its pre-scheduled time period. For example, unexpected news broadcasts, program cancellations, time overruns of previous live events, and other similar occurrences can result in an unscheduled delay or advance in the actual broadcast time of the desired program. Although information from an electronic programming guide (EPG) can be used to determine certain of these changes, the EPG may not be updated until after the user has programmed the recording device.
In these and other situations in which programs start early or end late relative to their pre-scheduled broadcast time period, the user recording a desired program using conventional techniques can inadvertently miss a significant portion of the program. For example, in the case of the two-hour movie noted above, a relatively short delay on the order of 5 to 15 minutes in the actual broadcast time period can cause the user to miss a crucial ending scene.
A number of techniques have been developed which attempt to solve the above-described problem. For example, U.S. Pat. No. 5,440,400, entitled xe2x80x9cDevice for Programming of Recording By Reference Signals Recognition,xe2x80x9d describes a technique which compares a stored reference picture with input video frames in order to detect the beginning of a program. However, the reference picture generally must be made available in some manner, e.g., via transmission in a broadcast stream. As a result, this technique is generally unable to provide suitable automatic detection of actual program start and end times.
U.S. Pat. No. 5,659,653, entitled xe2x80x9cMethod for Programming a Recording Device and Programming Device,xe2x80x9d describes a technique in which program-related data transmitted in the broadcast stream are evaluated and stored when a user presses a LEARN button on a remote control. The program-related data identifies the broadcast time, date and channel of a corresponding program, and the extracted data is used to program a VCR to record that program. This technique allows a user to select a given program for future recording when a commercial for that program is aired prior to the broadcast of the program. However, it generally requires that the program-related data be broadcast to the user, and therefore cannot be implemented in a fully automatic manner, e.g., without the need for a broadcast provider to insert additional information into the broadcast.
U.S. Pat. No. 5,758,009, entitled xe2x80x9cVideo Recording Control Device,xe2x80x9d describes a technique in which a recording device is controlled based on elapsed broadcast time information of a program, as contained in an Extended Data Service (EDS) signal superimposed on a received television signal during its vertical blanking interval. Again, this technique requires the insertion of additional information into the broadcast, and therefore cannot be implemented in a fully automatic manner.
As is apparent from the above, a need exists for improved techniques for controlling video recording devices such that recording of a given program can begin prior to or extend beyond a preset recording time period.
The invention provides improved techniques for controlling the recording of broadcast programs.
In accordance with the invention, a video signal is processed to generate one or more signatures associated with a broadcast program to be recorded by a recording device. The signatures are then further processed, e.g., compared with known stored information regarding the broadcast program, so as to determine an actual start time and end time of the program. One or more of the extracted signatures may be based at least in part on, e.g., a keyframe similarity measure, a color histogram or other type of feature histogram, one or more detected commercials, a transcript, a program logo or other detected object, detected text, and a sign-on or sign-off of the desired program, as well as appropriately weighted combinations of these and other features of the broadcast program.
Advantageously, the invention allows the precise start and end times of broadcast programs to be determined, such that a recording device can be controlled to record the programs in their entirety despite delays or other changes in pre-scheduled broadcast time slots. Unlike conventional techniques, the invention does not require a broadcast provider to insert any additional information in the broadcast. The techniques of the invention can therefore be implemented in a fully automatic manner, using only the existing information already present in the broadcast. These and other features and advantages of the present invention will become more apparent from the accompanying drawings and the following detailed description.